J Food Bioact

Journal of Food Bioactives, ISSN 2637-8752 print, 2637-8779 online

Journal website www.isnff-jfb.com

Review

Volume 19, September 2022, pages 143-153

Antidiabetic effect of Melicope glabra (Blume) T.G. Hartley (Rutaceae) in high-fat diet/streptozotocin-induced diabetic rats and its bioactive components

Figure 1. The effects of M. glabra extract on blood glucose levels in OGTT. Data are shown as mean ± standard deviation. *(p < 0.05) versus normal control; ^#(p < 0.05) versus diabetic control. a (p < 0.05) versus FBG at 30 min. 50MG: Group received 50 mg/kg of M. glabra extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; SITA: Group received 10 mg/kg of sitagliptin.

Figure 2. The effects of M. glabra extract on AUC of glucose values at 0–120 min after glucose load of experimental rats. Data are shown as mean ± standard deviation. *(p < 0.05) versus normal control; ^#(p < 0.05) versus diabetic control. 50MG: Group received 50 mg/kg of M. glabra extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; SITA: Group received 10 mg/kg of sitagliptin.

**Table 1.** Effects of *M. glabra* leaves extract on body weight gain and selected liver and kidney function indices in acute toxicity study
Parameters	Animal Groups
Data are shown as mean ± standard deviation. (p < 0.05) versus Control. 2000MG: Group received 2,000 mg/kg of M. glabra* extract.
1st week body weight gain (%)	11.20 ± 2.13	11.60 ± 0.74
2nd week body weight gain (%)	11.62 ± 3.02	11.95 ± 2.24
ALT (U/L)	46.00 ± 5.14	45.31 ± 6.66
AST (U/L)	171.67 ± 19.08	172.12 ± 16.67
ALP (U/L)	202.00 ± 7.07	201.00 ± 8.38
Creatinine (μmol/L)	39.00 ± 2.36	40.00 ± 3.61
Urea (mmol/L)	9.20 ± 0.81	8.90 ± 1.15
Sodium (mmol/L)	148.33 ± 3.05	146.50 ± 1.53
Potassium (mmol/L)	5.10 ± 0.26	5.10 ± 0.21
Chloride (mmol/L)	102.67 ± 2.31	102.00 ± 1.00

Table 1. Effects of M. glabra leaves extract on body weight gain and selected liver and kidney function indices in acute toxicity study

Parameters

Animal Groups

Control

2000MG

Data are shown as mean ± standard deviation. *(p < 0.05) versus Control. 2000MG: Group received 2,000 mg/kg of M. glabra extract.

1st week body weight gain (%)

11.20 ± 2.13

11.60 ± 0.74

2nd week body weight gain (%)

11.62 ± 3.02

11.95 ± 2.24

ALT (U/L)

46.00 ± 5.14

45.31 ± 6.66

AST (U/L)

171.67 ± 19.08

172.12 ± 16.67

ALP (U/L)

202.00 ± 7.07

201.00 ± 8.38

Creatinine (μmol/L)

39.00 ± 2.36

40.00 ± 3.61

Urea (mmol/L)

9.20 ± 0.81

8.90 ± 1.15

Sodium (mmol/L)

148.33 ± 3.05

146.50 ± 1.53

Potassium (mmol/L)

5.10 ± 0.26

5.10 ± 0.21

Chloride (mmol/L)

102.67 ± 2.31

102.00 ± 1.00

**Table 2.** Body weight of experimental rats on 0, 14th, and 28th day of treatment period
Groups	Body weight (g)
Data are shown as mean ± standard deviation. (p < 0.05) versus NC; #(p < 0.05) versus DC. NC: Normal Control; DC: Diabetic control; 50MG: Group received 50 mg/kg of M. glabra* extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; SITA: Group received 10 mg/kg of sitagliptin.
NC	249.26 ± 5.04^#	259.41 ± 6.98	272.33 ± 6.24^#
DC	283.88 ± 6.83*	266.54 ± 4.97	252.67 ± 10.72*
50MG	275.77 ± 7.75*	271.91 ± 5.11	268.99 ± 8.13
100MG	273.56 ± 9.77*	275.78 ± 9.06	278.10 ± 9.97^#
200MG	284.82 ± 10.07*	288.40 ± 7.83*	297.36 ± 6.90^#*
SITA	272.42 ± 7.13*	279.06 ± 5.95	291.11 ± 6.64^#*

Table 2. Body weight of experimental rats on 0, 14th, and 28th day of treatment period

Groups

Body weight (g)

0 day

14^th day

28^th day

Data are shown as mean ± standard deviation. *(p < 0.05) versus NC; #(p < 0.05) versus DC. NC: Normal Control; DC: Diabetic control; 50MG: Group received 50 mg/kg of M. glabra extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; SITA: Group received 10 mg/kg of sitagliptin.

249.26 ± 5.04^#

259.41 ± 6.98

272.33 ± 6.24^#

283.88 ± 6.83*

266.54 ± 4.97

252.67 ± 10.72*

50MG

275.77 ± 7.75*

271.91 ± 5.11

268.99 ± 8.13

100MG

273.56 ± 9.77*

275.78 ± 9.06

278.10 ± 9.97^#

200MG

284.82 ± 10.07*

288.40 ± 7.83*

297.36 ± 6.90^#*

SITA

272.42 ± 7.13*

279.06 ± 5.95

291.11 ± 6.64^#*

**Table 3.** Fasting blood glucose (FBG) levels of experimental rats on 0, 14th, and 28th day of treatment period
Groups	Body weight (g)
Data are shown as mean ± standard deviation. a(p < 0.05) versus 0 day; (p < 0.05) versus normal control; #(p < 0.05) versus diabetic control. 50MG: Group received 50 mg/kg of M. glabra* extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; SITA: Group received 10 mg/kg of sitagliptin.
Normal Control	4.40 ± 0.17^#	4.43 ± 0.16^#	4.40 ± 0.10^#
Diabetic Control	22.87 ± 2.31*	23.80 ± 1.21*	24.47 ± 1.65*
50MG	20.93 ± 1.15*	20.27 ± 1.56*	19.63 ± 1.79*^#
100MG	22.47 ± 1.46*	21.28 ± 2.80*	19.32 ± 1.95^a*^#
200MG	20.87 ± 1.04*	17.94 ± 0.65^a*^#	15.52 ± 0.73^a*^#
SITA	23.50 ± 0.99*	17.01 ± 0.42^a *^#	14.60 ± 1.58^a*^#

Table 3. Fasting blood glucose (FBG) levels of experimental rats on 0, 14th, and 28th day of treatment period

Groups

Body weight (g)

0 day

14^th day

28^th day

Data are shown as mean ± standard deviation. a(p < 0.05) versus 0 day; *(p < 0.05) versus normal control; #(p < 0.05) versus diabetic control. 50MG: Group received 50 mg/kg of M. glabra extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; SITA: Group received 10 mg/kg of sitagliptin.

Normal Control

4.40 ± 0.17^#

4.43 ± 0.16^#

4.40 ± 0.10^#

Diabetic Control

22.87 ± 2.31*

23.80 ± 1.21*

24.47 ± 1.65*

50MG

20.93 ± 1.15*

20.27 ± 1.56*

19.63 ± 1.79*^#

100MG

22.47 ± 1.46*

21.28 ± 2.80*

19.32 ± 1.95^a*^#

200MG

20.87 ± 1.04*

17.94 ± 0.65^a*^#

15.52 ± 0.73^a*^#

SITA

23.50 ± 0.99*

17.01 ± 0.42^a *^#

14.60 ± 1.58^a*^#

**Table 4.** Serum DPP-4, GLP-1, and insulin levels of experimental rats
Groups	Parameters
Data are shown as mean ± standard deviation. (p < 0.05) versus NC; ^#(p < 0.05) versus DC. NC: Normal control; DC: Diabetic control; 50MG: Group received 50 mg/kg of M. glabra* extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; Sitagliptin: Group received 10 mg/kg of sitagliptin.
NC	3.76 ± 0.18^#	24.01 ± 1.59^#	4.36 ± 0.72^#
DC	4.96 ± 0.06*	7.50 ± 1.05*	1.29 ± 0.48*
50MG	4.48 ± 0.35*	8.57 ± 0.73*	1.82 ± 0.53*
100MG	4.34 ± 0.09*^#	10.04 ± 1.71*	2.35 ± 0.85*
200MG	4.13 ± 0.14*^#	13.05 ± 0.11*^#	2.87 ± 0.67*^#
Sitagliptin	4.06 ± 0.05^#	15.95 ± 0.75*^#	3.57 ± 0.09*^#

Table 4. Serum DPP-4, GLP-1, and insulin levels of experimental rats

Groups

Parameters

DPP-4 (ng/mL)

GLP-1 (pmol/L)

Insulin (ng/mL)

Data are shown as mean ± standard deviation. *(p < 0.05) versus NC; ^#(p < 0.05) versus DC. NC: Normal control; DC: Diabetic control; 50MG: Group received 50 mg/kg of M. glabra extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; Sitagliptin: Group received 10 mg/kg of sitagliptin.

3.76 ± 0.18^#

24.01 ± 1.59^#

4.36 ± 0.72^#

4.96 ± 0.06*

7.50 ± 1.05*

1.29 ± 0.48*

50MG

4.48 ± 0.35*

8.57 ± 0.73*

1.82 ± 0.53*

100MG

4.34 ± 0.09*^#

10.04 ± 1.71*

2.35 ± 0.85*

200MG

4.13 ± 0.14*^#

13.05 ± 0.11*^#

2.87 ± 0.67*^#

Sitagliptin

4.06 ± 0.05^#

15.95 ± 0.75*^#

3.57 ± 0.09*^#

**Table 5.** Serum lipid, liver, and kidney profile indices of experimental rats.
Parameters	Groups
Data are shown as mean ± standard deviation. (p < 0.05) versus NC; ^#(p < 0.05) versus DC. NC: Normal control; DC: Diabetic control; 50MG: Group received 50 mg/kg of M. glabra* extract; 100MG: Group received 100 mg/kg of M. glabra extract; 200MG: Group received 200 mg/kg of M. glabra extract; SITA: Group received 10 mg/kg of sitagliptin.
TC (mmol/L)	1.70 ± 0.08^#	2.85 ± 0.07*	2.13 ± 0.11*^#	2.04 ± 0.08*^#	1.86 ± 0.06*^#	1.90 ± 0.03*^#
TG (mmol/L)	0.51 ± 0.04^#	1.85 ± 0.07*	1.15 ± 0.01*^#	0.93 ± 0.06*^#	0.66 ± 0.06^#	0.78 ± 0.12^#
LDL (mmol/L)	0.21 ± 0.04^#	1.16 ± 0.13*	0.88 ± 0.10*^#	0.85 ± 0.06*^#	0.50 ± 0.07*^#	0.55 ± 0.09*^#
HDL (mmol/L)	1.45 ± 0.07^#	0.48 ± 0.06*	0.91 ± 0.09*^#	1.07 ± 0.11*^#	1.28 ± 0.10*^#	1.30 ± 0.02*^#
ALT (U/L)	28.93 ± 8.68^#	107.95 ± 9.69*	62.05 ± 8.70*^#	44.90 ± 13.58^#	32.35 ± 2.76^#	38.25 ± 2.05^#
AST (U/L)	81.97 ± 8.68^#	271.90 ± 39.17*	140.50 ± 10.61*^#	98.80 ± 8.77*^#	89.85 ± 1.06^#	86.85 ± 2.47^#
ALP (U/L)	54.57 ± 7.87^#	448.20 ± 11.31*	152.95 ± 13.08*^#	166.40 ± 12.87*^#	126.70 ± 16.83*^#	126.35 ± 7.57*^#
Urea (mmol/L)	5.28 ± 0.59^#	9.56 ± 1.34*	7.66 ± 0.18*	5.95 ± 0.37*^#	4.90 ± 1.12*^#	4.26 ± 0.86*^#
Creatinine (μmol/L)	34.80 ± 0.71^#	41.45 ± 0.64*	39.25 ± 1.48*	34.25 ± 0.07^#	34.90 ± 0.85^#	33.45 ± 2.62^#
Sodium (mmol/L)	146.50 ± 0.71^#	136.00 ± 1.41*	136.50 ± 0.71*	138.00 ± 1.41*	142.50 ± 0.71^#	149.00 ± 4.24^#
Potassium (mmol/L)	4.70 ± 0.42	4.60 ± 0.57	5.25 ± 0.64	4.95 ± 0.07	5.25 ± 0.35	4.95 ± 0.78
Chloride (mmol/L)	98.00 ± 2.83	94.50 ± 3.54	92.00 ± 1.41	97.00 ± 1.41	100.00 ± 5.66	96.50 ± 6.61

Table 5. Serum lipid, liver, and kidney profile indices of experimental rats.

Parameters

Groups

50MG

100MG

200MG

SITA

TC (mmol/L)

1.70 ± 0.08^#

2.85 ± 0.07*

2.13 ± 0.11*^#

2.04 ± 0.08*^#

1.86 ± 0.06*^#

1.90 ± 0.03*^#

TG (mmol/L)

0.51 ± 0.04^#

1.85 ± 0.07*

1.15 ± 0.01*^#

0.93 ± 0.06*^#

0.66 ± 0.06^#

0.78 ± 0.12^#

LDL (mmol/L)

0.21 ± 0.04^#

1.16 ± 0.13*

0.88 ± 0.10*^#

0.85 ± 0.06*^#

0.50 ± 0.07*^#

0.55 ± 0.09*^#

HDL (mmol/L)

1.45 ± 0.07^#

0.48 ± 0.06*

0.91 ± 0.09*^#

1.07 ± 0.11*^#

1.28 ± 0.10*^#

1.30 ± 0.02*^#

ALT (U/L)

28.93 ± 8.68^#

107.95 ± 9.69*

62.05 ± 8.70*^#

44.90 ± 13.58^#

32.35 ± 2.76^#

38.25 ± 2.05^#

AST (U/L)

81.97 ± 8.68^#

271.90 ± 39.17*

140.50 ± 10.61*^#

98.80 ± 8.77*^#

89.85 ± 1.06^#

86.85 ± 2.47^#

ALP (U/L)

54.57 ± 7.87^#

448.20 ± 11.31*

152.95 ± 13.08*^#

166.40 ± 12.87*^#

126.70 ± 16.83*^#

126.35 ± 7.57*^#

Urea (mmol/L)

5.28 ± 0.59^#

9.56 ± 1.34*

7.66 ± 0.18*

5.95 ± 0.37*^#

4.90 ± 1.12*^#

4.26 ± 0.86*^#

Creatinine (μmol/L)

34.80 ± 0.71^#

41.45 ± 0.64*

39.25 ± 1.48*

34.25 ± 0.07^#

34.90 ± 0.85^#

33.45 ± 2.62^#

Sodium (mmol/L)

146.50 ± 0.71^#

136.00 ± 1.41*

136.50 ± 0.71*

138.00 ± 1.41*

142.50 ± 0.71^#

149.00 ± 4.24^#

Potassium (mmol/L)

4.70 ± 0.42

4.60 ± 0.57

5.25 ± 0.64

4.95 ± 0.07

5.25 ± 0.35

4.95 ± 0.78

Chloride (mmol/L)

98.00 ± 2.83

94.50 ± 3.54

92.00 ± 1.41

97.00 ± 1.41

100.00 ± 5.66

96.50 ± 6.61

**Table 6.** DPP-4 and α-amylase inhibitory activities of isolated phytoconstituents of *M. glabra* leaves extract
Compounds	IC50 (μg/mL)
ND: Not detected where IC₅₀ exceeded concentration tested (1,000 μg/mL); NA: Not applicable. All values were expressed as mean ± standard deviation of triplicates. Data with different superscript (a, b, c, d) in the same column were considered significant (p < 0.05).
p-geranyl coumaric acid (1)	ND	ND
Stigmasterol (2)	ND	125.47 ± 6.69^b (304.02 ± 16.20 μM)
Scopoletin (3)	6.98 ± 0.53^b (36.34 ± 2.80 μM)	79.24 ± 3.52^a (412.36 ± 18.31 μM)
Evolitrine (4)	ND	ND
Pachypodol (5)	22.83 ± 0.79^c (66.34 ± 2.30 μM)	209.27 ± 17.19^d (608.20 ± 49.95 μM)
Sitagliptin	0.01 ± 0.01^a (0.03 ± 0.01 μM)	NA
Acarbose	NA	182.31 ± 6.42^c (282.38 ± 9.95 μM)

Table 6. DPP-4 and α-amylase inhibitory activities of isolated phytoconstituents of M. glabra leaves extract

Compounds

IC50 (μg/mL)

DPP-4

α-amylase

ND: Not detected where IC₅₀ exceeded concentration tested (1,000 μg/mL); NA: Not applicable. All values were expressed as mean ± standard deviation of triplicates. Data with different superscript (a, b, c, d) in the same column were considered significant (p < 0.05).

p-geranyl coumaric acid (1)

Stigmasterol (2)

125.47 ± 6.69^b (304.02 ± 16.20 μM)

Scopoletin (3)

6.98 ± 0.53^b (36.34 ± 2.80 μM)

79.24 ± 3.52^a (412.36 ± 18.31 μM)

Evolitrine (4)

Pachypodol (5)

22.83 ± 0.79^c (66.34 ± 2.30 μM)

209.27 ± 17.19^d (608.20 ± 49.95 μM)

Sitagliptin

0.01 ± 0.01^a (0.03 ± 0.01 μM)

Acarbose

182.31 ± 6.42^c (282.38 ± 9.95 μM)